Halocarbon based fluids have found widespread use in industry for solvent cleaning and solvents in aerosols for the degreasing and otherwise cleaning of solid surfaces, especially intricate parts and difficult to remove soils. Unfortunately, many of the properties that render these solvent mixtures attractive for degreasing also makes them highly flammable with flammability ratings according to the Globally Harmonized System (GHS) of labelling of Category 1 or 2. This category is defined by a flash point of greater or equal to 23° C. and less than or equal to 60° C., where the flash Point is determined by closed cup methods as provided in the GHS document, Chapter 2.5, paragraph 11. As a result of the flammability hazard, usage of such solvents is limited to a subset of the environments in which could be useful.
In its simplest form, vapor degreasing or solvent cleaning involves exposing a room temperature article to be cleaned to an aerosol spray or vapors of a boiling solvent. Vapors condensing on the article provide clean distilled solvent to wash away organic soils, such as grease or other contamination from the article. Final evaporation of solvent from the object carries much of the organic soil therewith and limits the amount of residue associated with simply washing the article in liquid solvent.
As it is difficult to find a single, pure solvent molecule that achieves all the desired goals of a degreasing solvent, blends are typically employed. With the use of degreasing solvents at to near boiling points for solvent mixture constituents, azeotropes have been extensively explored as the molecular level interactions associated with azeotropes precludes fractionation upon boiling. Often conventional degreasing solvents have tolerated higher levels of flammability in order to obtain the desired levels of stability and degreasing ability with lower cost constituents. However, there is a growing appreciation that reducing the flammability category of degreasing solvents produces health and safety benefits that cannot be treated as secondary considerations.
Additionally, reformulation of conventional degreasing solvents is of concern owing to the tropospheric ozone depleting properties of chlorofluorocarbons. The resulting limitations of the usage of such compounds favors usage of fluorocarbons. In this effort, 1,1,1,3,3-pentafluoropropane and chlorinated ethylenes (trans 1,2 dichloroethylene, methylene chloride, trichlorethylene, and mixtures thereof), have been investigated, yet the flammability and/or ignitability in confined spaces of such solvent mixtures remains problematic.
Thus, there exists a need for a degreasing composition that retains the solvency and environmentally tolerated properties of conventional degreasing compositions while reducing the GHS flammability category rating from category 1 or 2 to a category of non-flammable or not classified.